Recreational marine vehicles such as speedboats, ski boats, fishing boats, houseboats and the like commonly have a motor-driven drive system which includes a multi-bladed marine propeller. The propeller typically includes a hub from which extends multiple, spaced-apart propeller blades each having a leading face and a trailing face which is opposite the leading face. Each blade is oriented at an angle with respect to the rotational axis of the hub. Therefore, when the propeller is submerged in a lake or other water body on which the marine vehicle floats and is rotated in a first direction, the leading face of each propeller blade applies rearward pressure against the water, propelling the marine vehicle forwardly on the water body. Conversely, when the propeller is rotated in a second direction, the trailing face of each propeller blade applies forward pressure against the water, propelling the marine vehicle rearwardly on the water body.
One of the problems which is frequently encountered in operating a marine vehicle in reverse results from cavitation of the water at the trailing face of each blade on the propeller. As the submerged propeller is rotated in water, the water accelerates around the edges of each blade, causing a reduction in water pressure at the trailing face of the blade until the pressure of the water eventually reaches the vapor pressure of the water. Consequently, cavitation occurs at the trailing face of the blade as the water vaporizes and small bubbles of air form in the water. Cavitation of the water at the trailing face of each blade when the vehicle is operated in reverse typically results in vibration of the propeller and may compromise the reverse thrust capability of the marine vehicle.
Therefore, a marine propeller having a reverse thrust cup provided in each blade of the propeller to minimize cavitation and enhance the reverse thrust capability of the propeller is needed.